A comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxes

Handle URI:
http://hdl.handle.net/10754/594087
Title:
A comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxes
Authors:
Yee, Mei Sun; Pauwels, Valentijn R N; Daly, Edoardo; Beringer, Jason; Rüdiger, Christoph; McCabe, Matthew ( 0000-0002-1279-5272 ) ; Walker, Jeffrey P.
Abstract:
Accurate measurements of energy fluxes between land and atmosphere are important for understanding and modeling climatic patterns. Several methods are available to measure heat fluxes, and scintillometers are becoming increasingly popular because of their ability to measure sensible (. H) and latent (. LvE) heat fluxes over large spatial scales. The main motivation of this study was to test the use of different methods and technologies to derive surface heat fluxes.Measurements of H and LvE were carried out with an eddy covariance (EC) system, two different makes of optical large aperture scintillometers (LAS) and two microwave scintillometers (MWS) with different frequencies at a pasture site in a semi-arid environment of New South Wales, Australia. We used the EC measurements as a benchmark. Fluxes derived from the EC system and LAS systems agreed (R2>0.94), whereas the MWS systems measured lower H (bias ~60Wm-2) and larger LvE (bias ~65Wm-2) than EC. When the scintillometers were compared against each other, the two LASs showed good agreement of H (R2=0.98), while MWS with different frequencies and polarizations led to different results. Combination of LAS and MWS measurements (i.e., two wavelength method) resulted in performance that fell in between those estimated using either LAS or MWS alone when compared with the EC system. The cause for discrepancies between surface heat fluxes derived from the EC system and those from the MWS systems and the two-wavelength method are possibly related to inaccurate assignment of the structure parameter of temperature and humidity. Additionally, measurements from MWSs can be associated with two values of the Bowen ratio, thereby leading to uncertainties in the estimation of the fluxes. While only one solution has been considered in this study, when LvE was approximately less than 200Wm-2, the alternate solution may be more accurate. Therefore, for measurements of surface heat fluxes in a semi-arid or dry environment, the optical scintillometer is recommended, whereas further work will be required to improve the estimation of surface heat fluxes from microwave systems. © 2015 Elsevier B.V.
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division
Citation:
Yee MS, Pauwels VRN, Daly E, Beringer J, Rüdiger C, et al. (2015) A comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxes. Agricultural and Forest Meteorology 213: 226–239. Available: http://dx.doi.org/10.1016/j.agrformet.2015.07.004.
Publisher:
Elsevier BV
Journal:
Agricultural and Forest Meteorology
Issue Date:
Nov-2015
DOI:
10.1016/j.agrformet.2015.07.004
Type:
Article
ISSN:
0168-1923
Sponsors:
Japan Aerospace Exploration Agency
Appears in Collections:
Articles; Biological and Environmental Sciences and Engineering (BESE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorYee, Mei Sunen
dc.contributor.authorPauwels, Valentijn R Nen
dc.contributor.authorDaly, Edoardoen
dc.contributor.authorBeringer, Jasonen
dc.contributor.authorRüdiger, Christophen
dc.contributor.authorMcCabe, Matthewen
dc.contributor.authorWalker, Jeffrey P.en
dc.date.accessioned2016-01-19T13:21:17Zen
dc.date.available2016-01-19T13:21:17Zen
dc.date.issued2015-11en
dc.identifier.citationYee MS, Pauwels VRN, Daly E, Beringer J, Rüdiger C, et al. (2015) A comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxes. Agricultural and Forest Meteorology 213: 226–239. Available: http://dx.doi.org/10.1016/j.agrformet.2015.07.004.en
dc.identifier.issn0168-1923en
dc.identifier.doi10.1016/j.agrformet.2015.07.004en
dc.identifier.urihttp://hdl.handle.net/10754/594087en
dc.description.abstractAccurate measurements of energy fluxes between land and atmosphere are important for understanding and modeling climatic patterns. Several methods are available to measure heat fluxes, and scintillometers are becoming increasingly popular because of their ability to measure sensible (. H) and latent (. LvE) heat fluxes over large spatial scales. The main motivation of this study was to test the use of different methods and technologies to derive surface heat fluxes.Measurements of H and LvE were carried out with an eddy covariance (EC) system, two different makes of optical large aperture scintillometers (LAS) and two microwave scintillometers (MWS) with different frequencies at a pasture site in a semi-arid environment of New South Wales, Australia. We used the EC measurements as a benchmark. Fluxes derived from the EC system and LAS systems agreed (R2>0.94), whereas the MWS systems measured lower H (bias ~60Wm-2) and larger LvE (bias ~65Wm-2) than EC. When the scintillometers were compared against each other, the two LASs showed good agreement of H (R2=0.98), while MWS with different frequencies and polarizations led to different results. Combination of LAS and MWS measurements (i.e., two wavelength method) resulted in performance that fell in between those estimated using either LAS or MWS alone when compared with the EC system. The cause for discrepancies between surface heat fluxes derived from the EC system and those from the MWS systems and the two-wavelength method are possibly related to inaccurate assignment of the structure parameter of temperature and humidity. Additionally, measurements from MWSs can be associated with two values of the Bowen ratio, thereby leading to uncertainties in the estimation of the fluxes. While only one solution has been considered in this study, when LvE was approximately less than 200Wm-2, the alternate solution may be more accurate. Therefore, for measurements of surface heat fluxes in a semi-arid or dry environment, the optical scintillometer is recommended, whereas further work will be required to improve the estimation of surface heat fluxes from microwave systems. © 2015 Elsevier B.V.en
dc.description.sponsorshipJapan Aerospace Exploration Agencyen
dc.publisherElsevier BVen
dc.subjectEddy-covarianceen
dc.subjectEvapotranspirationen
dc.subjectLatent heaten
dc.subjectScintillometeren
dc.subjectSensible heaten
dc.titleA comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxesen
dc.typeArticleen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
dc.identifier.journalAgricultural and Forest Meteorologyen
dc.contributor.institutionDepartment of Civil Engineering, Monash University, Clayton, Australiaen
dc.contributor.institutionSchool of Geography and Environmental Science, Monash University, Clayton, Australiaen
dc.contributor.institutionSchool of Earth and Environment, University of Western Australia, Crawley, WA, Australiaen
kaust.authorMcCabe, Matthewen
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